1. Technical Field
The present disclosure relates to a touch detection device, a display device with a touch detection function, and an electronic apparatus that are capable of detecting an external proximity object based on change in an electrostatic capacitance.
2. Description of the Related Art
In recent years, display devices with a touch detection function produced by mounting a touch detection device called a touch panel on a display device such as a liquid crystal display device or integrating the touch panel and the display device have attracted attention. The display devices with the touch detection function display various button images or the like on the display device so as to enable pieces of information to be input using the various button images or the like instead of conventional mechanical buttons. The display devices equipped with the touch panel do not need an input device such as a keyboard, a mouse, and a keypad, so that use thereof expands not only in computers but also in personal digital assistants such as mobile phones.
There are several systems for touch detection operations including an optical system, a resistance system and so on. An electrostatic capacitance system, which has a relatively simple structure and capable of achieving low power consumption, tends to be employed in the portable terminals and the like, in particular. The electrostatic capacitance-type touch detection device has divided drive electrodes to which a display drive signal is applied in a display operation state and a touch detection drive signal is applied in a touch detection operation state, and has touch detection electrodes. Electrostatic capacitances are formed between divided drive electrodes and divided touch detection electrodes. The electrostatic capacitance-type touch detection device detects change in the electrostatic capacitances caused by contact or proximity of an external object, that is, detects change in a voltage waveform appearing on the touch detection electrodes so as to determine presence and absence of touch detection.
As an electrostatic capacitance-type touch detection device, there is a touch detection device including a plurality of detection electrodes that are arranged so as to oppose to a plurality of drive electrodes extending in parallel, be orthogonal to the extending direction of the drive electrodes, and extend in parallel. The touch detection device applies a drive voltage to each of the drive electrodes for scanning and executes touch detection based on voltage waveforms detected by the detection electrodes. The display devices with the touch detection function scans each of a large number of drive electrodes and executes the touch detection operation, resulting in occurrence of a problem that it takes time to scan the entire screen and detect coordinates touched with an external object.
Japanese Patent Application Laid-open Publication No. H02-171818 (JP-A-H02-171818) discloses a display device with a touch detection function that executes scanning by sequentially applying a drive signal to each of blocks which is consist of a plurality of adjacent drive electrodes in order to solve the above-mentioned problem. The display device with the touch detection function as described in JP-A-H02-171818 executes scanning for each block so as to reduce time taken to scan the entire screen and detect coordinates touched with an external object in comparison with the case where it scans each drive electrode and executes the touch detection operation.
Furthermore, Japanese Patent Application Laid-open Publication No. 2010-92275 (JP-A-2010-92275) discloses a display device with a touch detection function that executes scanning by sequentially applying a drive signal to each of blocks which is consist of a plurality of adjacent drive electrodes. Scanning operation is done by shifting the block, to which drive signal is applied, to a subsequent block, and executes the touch operation detection.
The display device with the touch detection function as described in JP-A-H02-171818 cannot detect movement (change in coordinates) in the parallel arrangement direction of the drive electrodes in each block in a touch detected state. This causes a possibility that the accuracy of position detection is lowered.
Furthermore, the display device with the touch detection function as described in JP-A-2010-92275 executes scanning by applying the drive signal to each of blocks, so that touch sensitivity to the external object can be improved. On the other hand, the display device with the touch detection function shifts the block to be scanned for each electrode. That is, time taken to scan the entire screen and detect coordinates touched with the external object is the same as that in the case where scanning is executed for each electrode. Due to this, there is a possibility that the above-mentioned problem of taking time still remains.
For the foregoing reasons, there is a need for a touch detection device, a display device with a touch detection function, and an electronic apparatus that are capable of reducing the scanning time of entire screen, while suppressing a decrease in the accuracy of the position detection.